Commutator switch



1964 J. L. KING 3,146,323

COMMUTATOR SWITCH Filed g- 1961 2 Sheets-Sheet l ;17//////. H H r 104 INVENTOK JAMES L. KING FIG. 4 P

fink/ M- ATTORNEYS Aug. 25, 1964 J. L. KING 3,146,323

COMMUTATOR SWITCH Filed Aug. 15, 1961 2 Sheets-Sheet 2 INVENTOR. FIG 5 JAMES L. KING ATTORNEYS United States Patent 3,146,323 COMMUTATOR SWITCH James L. King, Sudbury, Mass., assignor to Acton Laboratories, Inc., a corporation of Massachusetts Filed Aug. 15, 1961, Ser. No. 131,573 12 Claims. (Cl. '20023) This invention relates to rotary switches and more particularly to commutators especially suitable for use in airborne telemetry systems.

Recent developments in rocket, satellite, missile, and aircraft technology have placed increasingly exacting requirements on airborne telemetry systems. While the challenge of these requirements has been particularly well met in almost all areas, there has existed the need for an improved commutator suitable for time-division multiplexing or sampling of data under diverse conditions, including vibration, shock, rapid acceleration and deceleration, and sharply varying temperatures and pressures. In addition to the need for extreme reliability under the foregoing conditions, the commutator must be small, light weight, relatively reasonable in cost, be flexible in programming, and have :a very low sign-al-to-noise ratio. Heretofore, most commutators have been completely customized for a particular job, and there has not been available an olf-the-shelf item that could be relatively easily modified for almost all commutator applications. Consequently, availability for comparatively large orders has been a matter of months rather than simply a matter of weeks or days. Moreover, previous commutators have suffered from a relatively high signal-to-noise ratio. In this connection, it is to be noted that for deep space probes, which now place definite limits on information rates, the internal and external noise sources are becoming the limiting factors. Near elimination of noise in commutation is a necessary step if accuracy in measurement is to be improved.

Accordingly, the primary object of the present invention is to provide a long-life, relatively low-noise, lowtorque, high-speed commutator switch which is exceptionally rugged and meets critical space and weight requirements of airborne telemetry systems. Commutators constructed according to the present invention comprise a unitary housing embodying an electric motor which rotates a contact depressor by means of a unique drive arrangement. The depressor places pressure against a flexible contact diaphragm which forms part of a switch capsule which consists of the aforementioned contact diaphragm and a switch plate comprising a stiff backing with a plurality of copper-clad switch segments arranged on one side thereof. The diaphragm is mounted in parallel closely spaced relation to the switch plate. Rotation of the depressor forces successive portions of the contact diaphragm into engagement with the successive switch segments. The contact diaphragm and the switch segments are connected to separate terminals of a multi-pin connector which is mounted in the housing. The number of segments on the switch plate can be modified easily, two typical installations having switch segments for thirty and sixty information channels. Depressors for one or two capsules may be operated from a single worm and worm gear drive.

Other objects and many of the attendant advantages of the present invention will become more readily apparent as reference is had to the following detailed specification when considered together with the accompanying drawings wherein:

FIG. 1 is a perspective view of a commutator constructed according to the present invention;

FIG. 2 is a plan view, with certain parts broken away, of a switch capsule which forms part of the commutator .of FIG. 1;

3,146,323 Patented Aug. 25, 1964 FIG. 3 is a sectional view of the switch disk forming part of the capsule of FIG. 2;

FIG. 4 is a sectional view taken along line 4--4 of FIG. 1; and

FIG. 5 is an exploded perspective view of the unit of FIG. 1.

Turning now to FIGS. 1 and 5, the illustrated commutator comprises a rectangular housing 2 formed from a single solid block of material. Preferably the housing is formed of aluminum and is finished by anodizing. The housing may also be fabricated from other materials having suitable physical properties. Housing 2 has a top wall 4, a bottom wall 6, and four side walls 8, 10, 12, and 14, in the order named. A large circular bore 16 is formed in the block, extending between and through upper wall 4 and bottom wall 6. Bore 16 is countersunk at both ends so as to form shoulders 20 and 22 for seating of identical covers 24 and 26. The covers are secured in place by screws 28 received in tapped holes 30.

The housing 2 is further formed with cavities in the side walls 12 and 14. Side wall 12 is provided with a large cavity 32 which is sutficiently deep so as to form an opening 36 communicating with the bore 16. In the illustrated embodiment, cavity 32 is sized to accommodate two connectors 4d and 42 of the multi-pin variety. These connectors are secured to the housing by thumb screws 44 which screw into suitable tapped holes 46 formed in side Wall 12. Two multi-pin connectors 40 and 42 are provided since two switch capsules are embodied in the commutator. Where only a single switch capsule is required, cavity 32 will be made smaller so as to accommodate a single multi-pin connector.

The adjacent wall 14 of the housing is provided with a rectangular cavity 48 sized to receive a smaller multi-pin connector 50. The same wall is provided with a circular bore 52 which extends into the housing a distance sulficient to fully accept a small electric motor 54. At the inner end of bore 52 there commences a second bore 56 of smaller dimension. Bore 56 intersects bore 16 along a chord of the circular periphery of the latter, so as to leave a connecting hole 58. Bore 56 is sized to accept a worm 62 mounted on the end of the output shaft of motor 54.

The connector 50 is attached to a cover plate 64 which fits into the wall 14 in covering relation to cavities 48 and 52. Connector 50 is attached to wall 64 by means of a pair of thumb screws 66, and plate 64 is attached to the housing by means of a screw 70 (FIG. 1) which is received by a tapped hole 72 formed at the base of rectangular cavity 48. It is to be observed that between cavity 43 and bore 52 there exists a wall or partition 76. The forward edge of this partition is cut back as indicated at 78 so as to form a passageway for leads connecting selected pins of connector 50 with terminals 80 on motor 54. Power is supplied to motor 54 via connector 50.

Positioned within the bore 16 is a spacer 84 of circular configuration. The spacer 84 is short of a complete cylinder, having a portion cut away as shown at 86. Spacer 84 is oriented so that the split therein is in registration with opening 58, thereby providing a passageway for worm 62. Spacer 84 also is grooved at its top and bottom edges so as to form shoulders 92 and 94 which act to support the switch capsules.

Although these capsules are constructed in the same manner, they may differ in the number of switch segments. However, for convenience, let it be assumed that capsules 8-8 and are identical even as to the number of switch segments, in which case, a description of capsule 88 will suffice also as a description of capsule 90.

As seen in FIGS. 2, 3 and 4, the capsule 88 includes an annular switch plate 98 formed of relatively stiff insulating material havingon its upper surface a plurality of switch contacts in the form of wedge-shaped conductive segments 100 and also a terminal contact in the form of a square-shaped segment 102 which is located between two of the segments 100. Preferably, these segments are formed by fully coating the surface of the switch plate 98 with a layer of copper, then silver-plating the copper coating, and finally etching away the coating so as to leave the aforesaid discrete segments. The switch plate also includes separate rivet-type soldering terminals 104 for each of the contact segments 100 and also segment 102. Positioned upon and adhesively secured to the segments are two annular standoff rings 106 and 108 formed of insulating material. Mounted on and supported by these standoff rings is a flexible contact diaphragm 110. This contact diaphragm consists of a layer of gold foil 112 adhesively secured to a flexible backing 114 consisting of a Teflon impregnated fabric formed of glass fibers. Further details on the construction of the contact diaphragm and variations thereof are presented in US. Patent No. 2,862,089, issued November 25, 1958, to William I. Mairs, which relates to potentiometers.

The contact diaphragm is adhesively secured to the standoff rings. The diaphragm is supported by the two rings in such a manner that the portion thereof that bridges the two standoff rings is in parallel spaced relation with the contact segments of the switch plate. Thus, in the absence of any depressing force, the contact diaphragm does not make electrical contact with the conductive switch segments 100. However, the contact diaphragm 110 does make contact with the small squareshaped terminal segment 102. In this connection, it is to be observed that the foil of the diaphragm has a radial extension 116 which is secured to the segment 102 by a suitable conductive cement or by soldering. Although not shown, it is to be noted also that potting may be applied over exposed portions of segments 100 along the inner and outer margins of the capsule to act as a barrier against moisture and also to prevent electrical breakdown.

The terminals 104 are connected to the pins of the connectors 40 and 42 by appropriate insulated leads 118. These leads are soldered to the terminals 104 before the capsules are inserted in the housing 2 and are soldered to the pins of the connectors 40 and 42 only after the capsules have been mounted within the housing. Cavity 32 is sufficiently large to accommodate slack portions of leads 118.

The two capsules 88 and 90 are adhesively secured to spacer 84 which is adhesively secured to the surface defining bore 16. However, before they are attached to the spacer, there is added therebetween a depressor assembly identified generally at 120. This assembly comprises a worm gear 122 having removable hubs 124 at opposite sides thereof. These hubs are secured to the gear by screws 126 which are received by tapped holes provided in the gear. Each hub 124 is provided on its undersurface with a diametrically extending slot 130 sized to snugly receive the rectangular body section of a resilient depressor member 134. These depressor members are clamped between hubs 124 and gear 122. Each depressor member has a hole 136 sized to receive a stub shaft 138 (FIG. 4) and also includes an offset or bent finger 140. The resilient finger 140 is provided with a hemispherical contact button 142. Each finger 140 is offset from gear 122 so its contact 142 will press against the diaphragm of the adjacent switch capsule. Gear 122 is mounted on stub shaft 138 by means of radial set screws (not shown) in each hub. Shaft 138 extends through the center holes of the two capsules 88 and 90, and its ends are provided with anti-friction bearings 144 and 146. The two covers 24 and 26 are provided with circular flanges 148 and 150 which define recesses in which the outer races of bearings 144 and 146 make a press fit when the covers are positioned flush with the outer surfaces of the housing. When the covers are secured in place by screws 28, shaft 138 is free to rotate but cannot shift axially or'"laterally. When gear 122 is rotated, depressors 134 will track in a circle along their respective contact diaphragms, forcing the latter to engage successive switch segments in turn. As a consequence, successive segments in turn will be connected briefly to the contact segment 102.

It is to be observed that depressors 134' will rotate at a fraction of the rate of rotation of the output shaft of motor 54 since worm 62 and gear 122 together constitute a gear reduction unit. This is a decided advantage in that it makes possible the use of conventional, readily gvailable and dependable high-speed, low-torque motors It is to be observed that the spacer 84 may be permanently secured within the housing 2 by means of removable fasteners instead of an adhesive or potting compound. Thus, for example, the spacer may be secured in place by means of screws received in tapped holes in the inner surface which defines bore 16. The use of screws instead of potting facilitates disassembly of the commutator for inspection purposes.

It is to be noted also that the commutator may be held in its place of installation by various fastening devices, as, for example, by screws or bolts passing through the housing via suitable holes 154. The commutator may be secured to a bracket or panel and may even be secured to other commutators so as to form a multi-unit assembly.

Commutators constructed as described have many advantages. For one thing, they are small and compact. Commutators have been constructed measuring 3 x 3% x 1 inches. Another advantage is that they lack conventional slip rings which wear out and induce drag. A further advantage is that the motor is a component part of the commutator, thereby allowing the entire drive system to be tested at the factory and avoiding the need for special adapters for connecting the unit to a separate motor at the time it is to be installed. Having the motor in the housing also allows the commutator to be constructed as a discrete plug-in module, thereby saving installation costs. Another advantage of the commutators constructed as described above is that they have a very low noise level. In practice, they have been found capable of handling satisfactorily signals as low as 50 microvolts. Because of this capability, it is not necessary to provide amplification stages prior to commutation, thereby resulting in considerable savings of Weight and space, especially where 30 or more signal channels are involved. The low noise level is due to the construction of the switch capsules, the manner in which they are mounted and wiped, the manner of mounting the motor, 312 the manner of mounting and driving the worm gear Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. Thus, for example, the form of the depressor member 134 may be changed so as to employ a roller contact instead of the fixed hemispherical button contact 138. The roller contact would comprise a roll member rotatably mounted on one end of a small shaft with the other end of the latter welded to the free end of finger 140. It is to be understood, therefore, that the invention is not limited in its application to the details of construction and arrangement of parts specifically described or illustrated, andthat within the scope of the appended claims, it may be practiced otherwise than as specifically described or illustrated.

I claim:

1. A commutator comprising a housing having a first bore, a first switchcapsule disposed within said bore, said first switch capsule comprising an annular switch plate having a circular array of conductive contact segments on one planar surface thereof and a resilient annular contact diaphragm supported at its inner and outer edges in parallel spaced relation to said segments and said planar surface, a rotatable stub shaft mounted wholly within said housing, said shaft extending through the center of said capsule, a worm gear secured to said shaft in said first bore, a diaphragm depressor member attached to and rotatable with said gear, said depressor member continually depressing some portion of said diaphragm into contact with a segment on said switch plate, a second bore in said housing, a worm mounted in said second bore in driving engagement with said gear, and means for driving said worm whereby to cause said depressor member to depress successive portions of said diaphragm into contact with successive contact segments.

2. A commutator as defined by claim 1 wherein said drive means comprises an electric motor contained wholly within said housing.

3. A commutator as defined by claim 1 wherein at least one end of said shaft is supported in a removable cover member closing off one end of said first bore.

4. A commutator as defined by claim 1 further including a multi-pin connector mounted in a side wall of said housing, and means connecting said contact segments to different pins of said connector.

5. A commutator as defined by claim 4 wherein said connector is mounted in a cavity in said side wall and said connecting means are Wire leads which extend through a hole directly connecting said first bore and said cavity.

6. A commutator as defined by claim 1 further including a second switch capsule with said gear disposed between said first and second capsules, and a second diaphragm depressor member attached to said gear in position so as to continually depress some portion of the diaphragm of said second switch capsule into contact with a contact segment of said second switch capsule.

7. A commutator comprising a polyhedral housing having generally rectangular top and bottom surfaces, said housing having a first bore parallel to said top and bottom surfaces and a second bore perpendicular to said top and bottom surfaces, said second bore partially intersecting said first bore, a worm rotatably disposed in said first bore, a worm gear rotatably disposed in said second bore in meshing relation with said worm, a resilient depressor member attached to said worm gear and rotatable therewith, and an annular switch capsule mounted in said second bore in parallel relation with said gear, said switch capsule comprising a switch plate having a flat surface with an array of discrete conductive contact segments thereon and an annular flexible contact diaphragm secured at its edges to said switch plate in parallel spaced relation to said contact segments and said fiat surface, said switch capsule disposed so that said resilient depressor member continually presses some portion of said diaphragm into engagement with one of said segments, whereby when said worm is rotated said resilient depressor member will depress successive portions of said diaphragm into engagement with successive segments.

8. A commutator as defined by claim 7 wherein said contact diaphragm comprises a resilient backing of insulating material and a conductive layer on said backing in facing relation to said segments.

9. A commutator as defined by claim 8 further including a multi-pin connector mounted in a side cavity in said housing, said side cavity communicating with said second bore, and wire leads connecting said conductive layer and said segments to pins of said connector.

10. A commutator as defined by claim 7 further inoluding a motor for driving said worm, said motor mounted entirely within said housing.

11. A commutator as defined by claim 7 wherein said second bore is open at one of said top and bottom surfaces, and further including a removable cover closing off the upper end of said bore.

12. A commutator as defined by claim 11 wherein said gear is mounted on a shaft contained wholly within said second bore.

References Cited in the file of this patent UNITED STATES PATENTS 2,602,865 Maurer July 8, 1952 2,773,951 Finley Dec. 11, 1956 2,855,473 Rabinow Oct. 7, 1958 FOREIGN PATENTS 7,004 Great Britain June 25, 1908 

1. A COMMUTATOR COMPRISING A HOUSING HAVING A FIRST BORE, A FIRST SWITCH CAPSULE DISPOSED WITHIN SAID BORE, SAID FIRST SWITCH CAPSULE COMPRISING AN ANNULAR SWITCH PLATE HAVING A CIRCULAR ARRAY OF CONDUCTIVE CONTACT SEGMENTS ON ONE PLANAR SURFACE THEREOF AND A RESILIENT ANNULAR CONTACT DIAPHRAGM SUPPORTED AT ITS INNER AND OUTER EDGES IN PARALLEL SPACED RELATION TO SAID SEGMENTS AND SAID PLANAR SURFACE, A ROTATABLE STUB SHAFT MOUNTED WHOLLY WITHIN SAID HOUSING, SAID SHAFT EXTENDING THROUGH THE CENTER OF SAID CAPSULE, A WORM GEAR SECURED TO SAID SHAFT IN SAID 